fix cron store backup churn (#19484)

src/cron/store.test.ts

@@ -2,7 +2,8 @@ import fs from "node:fs/promises";
 import os from "node:os";
 import path from "node:path";
 import { afterEach, describe, expect, it, vi } from "vitest";
-import { loadCronStore, resolveCronStorePath } from "./store.js";
+import { loadCronStore, resolveCronStorePath, saveCronStore } from "./store.js";
+import type { CronStoreFile } from "./types.js";
 
 async function makeStorePath() {
   const dir = await fs.mkdtemp(path.join(os.tmpdir(), "openclaw-cron-store-"));
@@ -15,6 +16,27 @@ async function makeStorePath() {
   };
 }
 
+function makeStore(jobId: string, enabled: boolean): CronStoreFile {
+  const now = Date.now();
+  return {
+    version: 1,
+    jobs: [
+      {
+        id: jobId,
+        name: `Job ${jobId}`,
+        enabled,
+        createdAtMs: now,
+        updatedAtMs: now,
+        schedule: { kind: "every", everyMs: 60_000 },
+        sessionTarget: "main",
+        wakeMode: "next-heartbeat",
+        payload: { kind: "systemEvent", text: `tick-${jobId}` },
+        state: {},
+      },
+    ],
+  };
+}
+
 describe("resolveCronStorePath", () => {
   afterEach(() => {
     vi.unstubAllEnvs();
@@ -43,4 +65,30 @@ describe("cron store", () => {
     await expect(loadCronStore(store.storePath)).rejects.toThrow(/Failed to parse cron store/i);
     await store.cleanup();
   });
+
+  it("does not create a backup file when saving unchanged content", async () => {
+    const store = await makeStorePath();
+    const payload = makeStore("job-1", true);
+
+    await saveCronStore(store.storePath, payload);
+    await saveCronStore(store.storePath, payload);
+
+    await expect(fs.stat(`${store.storePath}.bak`)).rejects.toThrow();
+    await store.cleanup();
+  });
+
+  it("backs up previous content before replacing the store", async () => {
+    const store = await makeStorePath();
+    const first = makeStore("job-1", true);
+    const second = makeStore("job-2", false);
+
+    await saveCronStore(store.storePath, first);
+    await saveCronStore(store.storePath, second);
+
+    const currentRaw = await fs.readFile(store.storePath, "utf-8");
+    const backupRaw = await fs.readFile(`${store.storePath}.bak`, "utf-8");
+    expect(JSON.parse(currentRaw)).toEqual(second);
+    expect(JSON.parse(backupRaw)).toEqual(first);
+    await store.cleanup();
+  });
 });

src/cron/store.ts

@@ -50,13 +50,26 @@ export async function loadCronStore(storePath: string): Promise<CronStoreFile> {
 export async function saveCronStore(storePath: string, store: CronStoreFile) {
   await fs.promises.mkdir(path.dirname(storePath), { recursive: true });
   const { randomBytes } = await import("node:crypto");
-  const tmp = `${storePath}.${process.pid}.${randomBytes(8).toString("hex")}.tmp`;
   const json = JSON.stringify(store, null, 2);
-  await fs.promises.writeFile(tmp, json, "utf-8");
-  await fs.promises.rename(tmp, storePath);
+  let previous: string | null = null;
   try {
-    await fs.promises.copyFile(storePath, `${storePath}.bak`);
-  } catch {
-    // best-effort
+    previous = await fs.promises.readFile(storePath, "utf-8");
+  } catch (err) {
+    if ((err as { code?: unknown }).code !== "ENOENT") {
+      throw err;
+    }
   }
+  if (previous === json) {
+    return;
+  }
+  const tmp = `${storePath}.${process.pid}.${randomBytes(8).toString("hex")}.tmp`;
+  await fs.promises.writeFile(tmp, json, "utf-8");
+  if (previous !== null) {
+    try {
+      await fs.promises.copyFile(storePath, `${storePath}.bak`);
+    } catch {
+      // best-effort
+    }
+  }
+  await fs.promises.rename(tmp, storePath);
 }